Converting 3D layer motion to camera.

So I'm making an earth zoom-in animation, I have a 3D layer moving towards the camera (as if camera is moving towards it), however I now realise I need the camera to be moving and not the 3D layer.

Is there a way to copy the movement keyframes from the 3D layer to the camera so the movement on screen appears the same?
i.e. I have the 3d layer moving towards camera.
I want the camera to move towards 3D layer without any change to the on-screen motion.

You might not need to use a camera; you can go into your graph editor, highlight the keyframes, go to your keyframe assistant (the little diamond icon) and set them for exponential scale. That way you will get a natural looking zooom in, as if it were camera movement.

That being said, this would be the difficulty with copying your keyframes and converting them to camera movements. I sometimes combine scaling up or down of footage items with camera movements to the right or left to achieve the result I am looking for, although I learned about a little button called "collapse transformation" which would allow me to do all this work with just the camera.

If that doesn't solve your problem, try moving the keyframes to a null object, and using it as an intermediary for parenting the camera properties to your null object.

Are you sure you need the cam to move and can't have the earth move? 99% of people watching it won't know the difference. But yes, just place your current time indicator at the first keyframe and select the property 'position' (the actual word, not keyframes) and copy. Select the camera's position property and paste, then select earth again and click on the stopwatch to remove the key frames from earth layer and it should be good to go. I did a test with a solid and a cam and it worked fine, kept the same timing and movement, but if it doesn't look right then just redo the cam movement, practice makes better!
-Keith

Yeah it is necessary to zoom the camera in instead of zooming the 3d layer, as I'm using some Particular effects which are parented to the 3D layer. So when the 3D layer moves towards the camera, because of the Particular trail effects parented to it, it is very apparent that the 3D layer is moving and not the camera.

The motion is quite complicated as I've parented the layer to a number of other layers (the camera needs to appear to be orbiting around a certain country after the zoom-in on earth), so it's not just a simple scale-up.

I think perhaps what might work is if I track the motion of the 3D layer using Mocha and then apply it to a camera, I think it won't be 100% accurate but it might work.